/Engine/Source/Runtime/AudioMixer/Public/AudioMixerDevice.h
Replace the submix effect of the given submix at the submix chain index with the new submix effect id and submix instance.
void ReplaceSoundEffectSubmix ( [USoundSubmix](API\Runtime\Engine\Sound\USoundSubmix) * InSoundSubmix, int32 InSubmixChainIndex, FSoundEffectSubmixPtr SoundEffect )